This invention relates generally to the field of devices used for sharpening lawn mower blades, and more particularly to the field of portable devices which allow the blade to be sharpened without removing the blade from the mower.
Lawn mowers comprising a gasoline or electric motor which rotates a cutting blade to shear the blades of grass are well known. The cutting blade in its most common configuration is centrally mounted on a generally vertical rotating axis or shaft and extends to either side of the shaft, such that two cutting edges are presented against the grass as the blade is rotated by the motor. The cutting edges are produced with a sharp or angled face in order to better bite and cut the individual grass blades. Over time, these cutting edges become dulled, and it is necessary to sharpen the cutting edges to maintain efficient operation. The frequency of the need for sharpening is determined by the amount of usage and type of grass and debris encountered by the mower. While a home owner may be able to mow for many months without noticing a drop in efficiency and cutting ability, commercial mowers which are in use daily and which may encounter roadside debris or other hard objects must be sharpened every few weeks or even more often. In order to sharpen the blade, it must be removed from the mower, which is usually accomplished by tipping the mower or the blade housing on its side and removing a bolt to free the cutting blade from the shaft. Removal of the bolt is often very difficult because dirt, grease and physical debris become entrapped in the threading. Once the cutting blade is removed, it is brought to a fixed grinding wheel, where the blade is sharpened on a rotating abrasive disk. To properly sharpen the blade, both the upper and lower side of the blade must be abraded. The blade is then returned to the mower and reattached. This method of sharpening creates a significant amount of downtime for the mower unless an extra blade is maintained so that the blades can be swapped in one operationxe2x80x94an issue not critical to the homeowner but very critical to commercial mowing businesses. Even with blade swapping, there remains the necessity to deliver the blade to the physical location of the grinding wheel.
It is an object of this invention to provide a device which addresses the problems of lawn mower blade sharpening discussed above. In particular, it is a object of this invention to provide a method and a device for sharpening the cutting blade of a lawn mower which does not require removal of the blade from the mower. It is a further object to provide such a method and device where the sharpening can be accomplished at remote locations, so that the mower does not need to be brought in from the field. It is a further object to provide such a method and device where the device is portable and easily operated. These objects and others not explicitly set forth in this paragraph are accomplished as expressed in the disclosure which follows.
The invention is in general a lawn mower blade sharpening device and a method of sharpening lawn mower blades using the device. The device comprises a motor to produce rotational movement of a flexible drive cable, where a two-sided grinding disk is attached to the drive cable such that operation of the motor rotates the grinding disk at a relatively high speed. The grinding disk is composed of a material suitable for removing metal from the dull mower blade in order to create a sharp edge. Preferably, a universal joint is provided between the flexible cable and the grinder body or grip to provide for maximum maneuverability of the grinding disk. The motor is preferably battery operated, but may also be electrically or gasoline operated. With this device, the lawn mower blade can be sharpened without the need to remove the blades from the mower, as the combination of flexible drive cable and two sided grinding wheel enable the operator to abrade both sides of the cutting blade to create a sharp edge.